Process of making metallic denture-backings



R. M. CRAIG.

PROCESS OF MAKING METALLIC DENTURE BACKING'S. APPLICATION FILED JUNE 19.1919.

1 53,565 Patented Sept. 21, 1926.

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Specification of Letters Patent. Pafl gntgd ggpt" 21 1920,

Application filed ,Iune 19, 1919., Seria1 N0.,305,421;.

To all whom it may concern: I

Be it known that I, ROBERT Mnann CRAIG, a citizen of the United States, residing at Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a certain new and useful Improvement in Processes of Making Metallic Denture- Baokings, whereof the following is a specification, reference being had to the accompan ing drawing.

y improvement relates to the manufacture of metallic backings for porcelain tooth ;bers of a single size may be used to form metallic backings of different sizes, by interposing more or less of the fusible element between them. However, that method of manufacture requires a great deal of time and skilled labor, and it is the object of my present invention to provide a method of quantity production of baokings each formed I of a single piece of pressed sheet metal, with the minimum amount of labor, by means of dies. Said single piece backing, and such die means, form the subject matter of other applications for Letters Patent of the United States copending herewith and respectively Serial Number 307,104, filed June-2?, 1919,

and Serial Number 398,590, filed July 3,

In accordance with my improved process, a primarily plane strip of sheet gold, or other suitable metal or alloy, of uniform thickness, is drawn through suitable dies to form a bar, having oppositev concave faces of substantially cylindriform curvature, so that the opposite longitudinal edges of said bar are about twice as thick as the middle portion thereof, throughout its length. Said bar is then divided to form plurality of backing'blanks, by similar successive punching operations, each of which produces a single blank of approximately rhombic con- 1'iguration, the shorter axis of which coin cides with the longitudinal axisof said bar. Each of saidblanks is then pressed, in suitable dies, so as to turn its thick edges upward, in substantially parallel relation, so that it is U-shaped in cross section, con sidered transversely with respect to the original bar. Such pressing operation contemporaneously arches said blank at its in termediate portion so that the exterior of the bight of the U is concavely curved in the direction of the length'of said bar, in con-' formity with the posterior portion ofthe porcelainbody which is to be embraced be tween the bifurcations of said backing.

My improved process produces a backing which differs from that shown'in my Letters Patent 1,221,420 not only in that it is formed of a single piece of sheet metal, instead of being formed of two pieces of cast metal, which must be fused in connec tion with an intermediatepiece; but alsoin that the web thereof intermediate of its side flanges is of uniform cross section throughout its length, .and thinner at its medial longitudinal axisthan at its opposite edges. Therefore, my improved process effects a material saving in gold, in comparison with that described in said Letters Patent 1221, 120; because the intermediate web of the three piece backing shown in the latter was not only of irregular. cross section throughout its length but of consider.- able thickness to insure theeifective ment of the fusible element.

Consequently, my improved process is advantageous, as compared with that disclosed in said Letters Patent, not only in that it produces a metallic backing of the specific class contemplated at great saving of skilled labor and consequent cost of manufacture; but with a substantial saving in the amount of precious metal required for a given backing. V

My invention includes the various novel features of procedure herein specified and claimed.

In said drawing; Figure I is a perspective view of a portion of a bar, produced from a primarily plane strip of sheet metal of uniform thickness, conveniently by a drawing operation.

Fig. II is a perspective view of a single backing blank punched from said bar.

Fig.- III isa perspective view of a shaped backing pressed from said blank;

the curved dash and dot line therein being engage-- in the plane of the longitudinal axis of the bar indicated by the dash and dot line in Fig. I, and indicating the extent to which the web intermediate of the bifurcations of said backing has been bent from its primarily straight form.

Fig. IV is a central longitudinal sectional View of said backing; the plane of section coinciding with the longitudinal axis of said bar indicated by the dash and dot line in Fig. I.

Fig. V is a plan View of said backing member in a denture representing a bicu'spid tooth, showing that the apposed flanges formed by the bifurcations of the U-shaped backing are closer together at their free edges than at their junction with said web, so as to form an undercut recess to receive denture.

Referring to Fig. I; the bar aforesaid has its opposite faces concavely and substantially cylindriforml curved throughout its length, so as to form a thin web'l with opposite thick longitudinal edges 2, of the same transverse cross section, throughout its 1 length. Such a bar is preferably formed by drawing a primarily plane and uniformly thick strip of sheet metal, between apposed die members; while said bar is progressed in the direction of its length. However, it is to be understood that such a bar as shown in Fig. I may be otherwise produced, instance, by a drop forging, or swaging, operation. Therefore, although 1- include the operation of drawing said bar as a step in one of the appended claims for my invention; I omit it from other claims, in which the preformation of such a bar, by any suitable method or means, is assumed.

The dotted lines shown in Fig. 1 indicate the outlines of respective backing blanks 3, which may besuccessively formed from said bar .by punching operations. it may be ob served that such outlines are of slightly greater extent, transversely with respect to said bar, than the width of the bar. That efiect is attained by such construction and arrangement of the punching dies that they not only cut each blank from aid bar, but c empcraneously swage it, so as to slightly reouce the thickness of the edges of said 3511. Such swaging operation not only spreads the blank 3 but makes the metal thereof more compact, so as to increase its stiffness to the degree which is desirable for the performan e of its function of retaining a porcelain body. In other words it is-tobe understood that it is preferable to employ metal in a state of maximum ductility to form the bar shown in Fig. I, because such condition of the metal facilitates whatever operation is employed to reduce the primarily plane sheet metal to the concave bar form, and it is also desirable to have the metal in a ductile state to facilitate the punching. operation by which the blanks are formed. However, it is desirable to have the metal in the finished backing in a less ductile state and, therefore, it is advantageous to so conduct the operations of producing said blank that the product has the desired clegree of stiffness to perform its function, and I prefer to attain said result by combining a swaging operation with the operation of punching said blanks as described. However, as all of the metals and alloys which are desirable to employ in making such backings are of the character in which the degree of rigidity thereof is directly related to the density thereof, attainable by compressing the metal; it is obvious that the desired degree of density of the metal'may be attained before the punching operation. Therefore, although I include the step of swaging the metal contemporaneously with the operation of punching it, in an appended claim, I do not desire to limit all of my claims to that specific step.

Referring to Fig. II; it may be observed that the backing blank 3 is of approximately rhombic outline, having its axis 4 corre spending with the longitudinal axis of said bar; so that the major portion of its area is formed of the thinner portions of said bar, only a fraction of said area being formed of the thickest, edge portions, of said bars Referring to Fig. Ill; it may be observed that the substantially Ushaped metallic backing, formed from said blank 3, has opposite side langes formed by the thick edges 2 aforesaid, bent so that they converge both from the bottom toward the top and from the intermediate web 1 toward the observer. Although said side flanges merge into said web directly at the upper edge of ti e latter; they merge into said web above the lower edge of the latter so as to leave a downwardly projecting portion 5, which, as hereinafter described, forms a locking flange for engagement with the porcelain facing to prevent the accidental escape of the latter from said backing. As it is intended that said flange 5 may be returned to the position shown in Figs. Ill and IV to permit said facing to be removed at any time; the metal of the blank thereat must be left in such ductile condition as to permit repeated fleXure, without fracturing it. That result is attained by confining the swaging operation aforesaid to the flanged portions of said blank. In other wo'rdsflny invention as defined in the most specific claim appended hereto has the advantage of producing a backing in which the metal is of different degrees of ductility at different regions thereof, in accordance with the par-' ticular stresses to whlch those reglons are" intended to be subjected.

Referring to Figs. V to VIII inclusive; the porcelain body, which forms the facing for the metallic backing aforesaid, comprises the anterior portion 7 and the posterior portion 8 in unitary Jrelation. Said anterior portion may be of any desired size, representing a natural tooth, and said posterior portion forms a dovetail 9 whereby said body is supported in and engaged by said metallic backing 10, which may form part of a plate, bridge, or other denture, to which it may be joinedby a soldering or other suitable operation.

As indicated by the dotted lines in Figs. V, VI and VIII; said dovetail 9 is wedge shaped in two directions at rightangles to -each other, its side faces'converging both from its occlusal end 11 to its gingival end 12 and from its lingual side 13 to its labial or buccal side 14, where it merges into the anterior portion 7 of said body; said converging faces being symmetrically disposed with respect to the central vertical plane of said porcelain body. Said posterior dovetail portion 9 is also converged and concavely curved longitudinally in its lingual face, from its gingival end toward its occlusal end, as best shown at 9 in Fig. VII. Said posterior portion 8 of said porcelain body being thus converged in three directions, as above described, is fitted in the correspondingly shaped recess in said metallic backing 10, the exterior contour 14: of which resembles that of the tooth imitated by the anterior portion 7 of said porcelain body.

The construction andvarrangement above described are such that the strains to which the denture is normally subjected viz., pressure in a directionfrom its occlusal or incisal end toward its gingivalend, and transversely from its lingual side to its labial side, merely serve to more firmly seat said porcelain body in its backing'lO. Although there is no'normal strain upon said denture tending to remove said porcelain body from its metallic backing in a direction from its gingival end'to its occlusal end, it may be manually slid and removed in that direction, without removing the backing from its setting, whenever it is desired to remove the porcelain body. Therefore,-although it is unnecessary to provide any special means for preventing such sliding movement in addition to the frictional engagement between said porcelain body and its backing, I prefer to provide said backing 10 with the unitary locking flange 5 which, when bent as indicated in dotted lines in Fig. IV, and in full and dotted lines in Fig. VII, normally prevents said porcelain body from thus sliding; sothat it is necessary to straighten said flange 5 to the position shown in fulllines in Fig; IVand in dotted lines in Fig. VII toremove said body. Therefore, said locking flange 5 may be repeatedly flexed to engage and disengage a porcelain body in saidbacking 10.

My present process also differs from that described in said Letters Patent 1,221,420 in,

that it is necessary to have dies 'of'respectively different sizes corresponding'with different sizes of natural teeth, to form the blanks shown in Fig. II and bend them as exemplified in Fig. III. However, the cost of such dies is negligible as compared with the great saving in cost of manufacture above contemplated. Moreover, a single I bar, such as shown in Fig.I, may be of such size and proportions that it may be used for all sizes of blanks required, and all sizes of porcelain bodies for a given tooth may be conveniently recessed alike, to receive the side flanges of metallic backings 10 as above described, so that the dies for forming the different sizes of the latterm'ay all be of one pattern, for a given tooth, except that they are of respectively different widths.

Therefore, I do not desire to limit inyself to the precise details of construction and arrangementherein set forth, as it is obvious that various modifications may be made therein without departing from the essential features of my-invention, as defined'in the appended claims.

1. In a process of making a metallic denture backing adapted to hold a "nonmetallio-:

tooth body; drawing a strip of primarily plane and uniformily thick sheet metal to a form a bar having opposite concave faces of substantially cylindriform curvature, so that the opposite longitudinal edges of said bar are thicker than the middle portion thereof, throughout its length; forming a blank of approximately rhombicconfiguration, by

punching the same from said bar, with the shorter axis of said blank coinciding with the'longitudinal axis of said bar, and 381- multane'ou'sly swaging said blanktoincrease its dimensions'transversely with respect to 7 said bar; thereby rendering the middle of said blank less-ductile at the regions swaged the intermediate web directly at one end of" the latter but terminate short of the opposite endof said web, leaving the latter projecting to forma locking flange; whereby the exterior of the bight of the U of said backing is concavely curved in the direction of the length of said bar, in conformity with the posterior portion of said nonmetallic' body which is to be embraced between the bifuractions of said backing, and said bifurcations form a recess which is wedge shaped in three directions, to wit, in respectively opposite directions longitudinally with respect to said arched portion thereof and in one direction transversely to said web, the web between said side flanges being wider at the end provided with said locking flange than at the other end, the space between the bifurcations of said backing being wider at its bight than at the free ends of said bifurcations, and the space be tween said bifurcations being wider at the end of said backing opposite said locking flange than intermediate of the length of said backing with respect to the axis of said bar.

2. In a process of making a metallic den- I ture backing adapted to hold a nonmetallic tooth body; drawing a strip of primarily plane and uniformly thick-sheet metal to form a bar having opposite concave faces, and opposite longitudinal edges thicker than'the middle portion thereof; forming a blank by punching the same from said bar, and simultaneously swaging said blank to increase its dimensions transversely with respect to said bar; thereby rendering the metal of said blank less ductile at the regions swaged than at the regions which are merely punched; pressing said blank so as to bend the thicker portions thereof transversely with respect to said thinner portion thereof, to form a backing which is U- shaped in cross section, considered trans versely with respect to said bar, the bifurcations thereof forming opposite side flanges which merge into the intermediate web directly at one end of the latter but terminate short of the opposite end of said web, leaving the latter projecting to form a locking flange; whereby said bifurcations form a recess which is wedge shaped in three direc tions, to wit, in respectively opposite directions longitudinally with respect to said arched portion thereof and in one direction transversely to said web, the web between said side flanges being wider at the end provided with said locking flange than at the other end, the space between the bifurcations of said backing being wider at its bight than at the free ends of said bifurcations, and the space between said bifurcations being wider at the end ofsaid backing opposite said locking flange than intermediate of the length of said backing with respect to the axis of said bar.

3. In a process of making a metallic denture backing adapted to hold a nonmetallic tooth body; drawing a strip of primarily plane and uniformly thick sheet metal to form a bar having opposite concave faces, and opposite longitudinal edges thicker than the middle portion thereof; forming a blank by punching the same from said bar; pressing said blank so as to bend the thicker portions thereof transversely with respect to said thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges which merge into the intermediate web directly at one end of the latter but terminate short of the opposite end of said web, leaving the latter projecting to form a locking flange; whereby said bifurcations vform a recess which is wedge shaped in three directions, to wit, in respectively opposite directions longitudinally with respect to said arched portion thereof and in one direction transversely to said web, the web between said side flanges being wider at the end provided with said locking flange than at the other end, the space between the bifurcations of said backing being wider at its bight than at the free ends of said bifurcations, and the space between said bifurcations being wider at the end of said backing opposite said locking flange than intermediate of the length of said backing with respect to the axis of said bar.

4:. In a process of making a metallic den ture backing adapted to hold a nonmetallie tooth body; working a strip of primarily plane and uniformly thick sheet metal to form a bar with opposite longitudinal edges thicker than the middle portion thereof; forming a blank by punching the same from said bar, and simultaneously swaging said blank to increase its dimensions transversely with respect to said bar; thereby rendering the metal of said blank less ductile at the regions swaged than at the regions which are merely punched; oressing said blank so asrto arch the thinner portion thereof in the direction of the axis of said bar, and bend the thicker portions thereof transversely with respect to said thinner portion thereof, to form a backing which is Ushaped in cross section, considered transversely with respect to said bar, the bifurcations thereof form ing opposite side flanges which merge into the intermediate web directly at one end of the latter but terminate short of the opposite end of said web, leaving the latter projecting to form a locking flange; whereby the exterior of the bight of the U of said back ing is concavely curved in the direction of the length of said bar, in conformity with the posterior portion of said nonmetallic body which is to be embraced between the bifurcations of said backing, and said bifurcations form a recess which is wedge shaped, the web between said side flanges being wider at one end than at the other end, and

the space between the bifurcations of said backing being wider at its bight than at the free ends of said bifurcations.

V 5. In a process of making a metallic denture backing adapted to hold a nonmetallic tooth body; working a strip of primarily plane and uniformly thick sheet metal to form a bar with opposite longitudinal edges thicker than the middle portion thereof; forming a blank by punching the same from said bar, and simultaneously swaging said blank to increase its dimensions transversely with respect to said bar; thereby rendering the metal of said blank less ductile at the regions swaged than at the regions which are merely punched; pressing said blank so as to arch the thinner portion thereof in the direction of the axis of said bar, and bend the thicker portions thereof transversely with respect to said thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges; whereby the exterior of the bight of the U of said back-' ing is concavely curved in the direction of the length of said bar, in conformity with the posterior portion of said nonmetallic body which is to be embraced between the bifurcations of said backing, and said bifurcations form a recess which is wedge shaped, the web between said side flanges being wider at one end than at the other end, and the space between the bifurcations of said backing being wider at its bight than at the free ends of. said bifurcations.

6. In a process of making a metallic denture backing adapted to hold a nonmetallic tooth body; working a strip of primarily plane and uniformly thick sheet metal to form a bar with opposite longitudinal edges thicker than the middle portion thereof;

forming a blank by punching the same from said bar; pressing said blank so as to arch the thinner portion thereof in the direction of the axis of said bar, and bend the thicker portions thereof transversely with respect to said thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges; whereby the exterior of the bight of the U of said backing'is concavely curved in the direction of the length of said bar, in conformity with the posterior portion of said nonmetallic body which is to be embraced between the bifurcations of said backing, and said bifurcations form a recess which is wedge shaped, the Web between said side flanges being wider at one end than at the other end, and the space between the bifurcations of said backing being wider at its bight than at the free ends of said bifurcations. V

7. In a process of making a metallic denture'backing' adapted to hold a nonmetallic tooth body; punching a bar having opposite longitudinal. edges thicker than themiddle portion thereof, to form a blank of approxi-' mately rhombic configuration, with the shorter axis of said blank coinciding with thelongitudinal axis of said bar, and-simultaneously swaging said jblanlr to-jincrease its dimensions transverselyiwith respect tosaid bar; thereby rendering-the metal of said blank less ductile at:the.re=

gions swaged than at theregions which are merely punched; presslngsaid blank sofas to arch the thinner portion thereof in'the direction of the axis of said bar, and bend the thicker portions thereof, to form abacking which is U-shaped in cross-sectiomc'onsidered transversely with respect to said bar, the bifurcations thereof forming oppor directions longitudinally with respect to said arched portion thereof. and in one direction transversely to said web, the web. between said sideflanges being wider atthe end provided with saidlocking flange than at the other end, the space between the .bifurcations of said backing being Wider at its bight than at the free ends-of said bifurcations and the space betweenl'said bifurcations being wider at the end of'said backing opposite said locking flange than intermediate of the length of said backing with respect tothe axis of said bar.

8. In a process of making a metallic denture backing adapted to hold a nonmetal-lie tooth body; punching a bar having opposite longitudinal edges thicker than the middle portion thereof,toform a blank of approximately rhombic configuration, with the shorter axis of said blank coinciding with the longitudinal axis ofsaid bar, and simultaneously swaging said blank to increase its dimensions transversely with respect to said bar; thereby rendering the middle of c said blank less ductile at the regions 'swaged than at the ,regions which are merely punched pressing said blank so as to arch the thinner portion thereof in'the direction of the axis of said bar, and bend the thicker bifurcations thereof forming opposite side.

i braced between the bifurcations of said backing, and said bifurcations form a recess which is wedge shaped in three directions, to wit,-in respectively opposite directions longitudinally with respect to said arched portion thereof and in one direction trans versely to said web,the web between said side flanges being wider at the end provided. with said locking flange than at the other end, the space between the bifurcations of said backing being wider at its bight than at thefree ends of said bifurcations and the space between said bifurcations being wider at the end of said backing opposite said locking flange than intermediate of the length of said backing with respect to the axis of said bar.

9. In a process of making a metallic denture backing adapted to hold a noninetall-ic tooth body; punching a bar having opposite longitudinal edges thicker than the middle portion thereof, to form a blank of approximately rhombic configuration, with the shorter axis of said blank coinciding with the longitudinal axis of said bar; press ing said blank so as to arch the thinner portion thereof in the direction of the aXis of said bar, and bend the thicker portions thereof transversely with respect to said thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges; whereby the exterior of the bight of the U of said backing is concavely curved in the direction of the length of said bar, in conformity with the posterior portion of said nonmetallic body which is to be embraced between the bifurcations of said backing, and said bifurcations form a recess'which is wedge shaped in three directions, to wit, in respectively opposite directions longitudinally with respect to said arched portion thereof and in one dirrection transversely to said web, the web between said side flanges being wider at the end provided with said locking flange than at the other end, the space between the bifurcations of said backing being wider at its bight than at the free ends of said bifurcations, and the space between said bifurcations being wider at the end of said backing 0pposite said locking flange than intermediate of the length of said backing with respect to the axis of said bar.

10. In a process of making a metallic denture backing adapted to hold a nonmetallic tooth body; forming a blank of approxi IHEL EQlTVThOIHblC configuration, by punching the same from a bar, with the shorter axis cations thereof forming opposite side liar thereof, to form a backing which is oof said blank coinciding with the longitudinal axis of said bar; pressing said blank so as to arch the thinner portion thereof in the direction of the aXis of said bar, and bend the thicker portions thereof trans-- versely with respect to said thinner portni-u thereof, to form a backing which is U- shaped in cross section, considered i'iransversely with'respect to said bar; the bifurwith an intermediate recess which is wed shaped in three directions, to wit, in two opposite directions longitudinally with spect to said bar axis and in one direction transversely to said axis; web bet said side flaages being wider at one 4 than at the other end, and said rec ss be tween said bifurcations being wider at their bight than at the free ends of said bifurcations.

11, In a process of making a metallic denture backing adapted to hold a nonmetallic tooth body; forming a blank by punching the same from a bar; pressing said blank so as to arch the thinner portion thereof in the direction of the axis of said bar, and

bend the thicker portions thereof transversely with respect to said thinner portion shaped in cross section, considered transversely with respect to said bar; the bifurcations thereof forming opposite side flanges with an intermediate recess which is wedge shaped in three directions, to wit, in two opposite directions longitudinally with respect to said bar axis and in one direction transversely to said axisythe web between said side flanges being wider at one end than at the other end, and said recess between said bifurcations being wider at their bight than at the free ends of saidbifurcations.

12. In a process of making a metallic denture'backing adapted to hold a nonmetallic tooth body; forming a bar having opposite concave faces of substantially cylindriform curvature, with opposite longitudinal edges thicker than the middle portion thereof, throughout its length; forming a blank by punching the same from said bar; pressing said blank so as to arch the thinner portion thereof in the direction of the axis of said bar, and bend the thicker portions thereof transversely with respect to the thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges for retaining said tooth body.

13. In a process of making a metallic denture backing adapted to hold a nonmetallic tooth body; forming a bar having opposite concave faces of substantially cylindriform curvature, with opposite longitudinal edges thicker than the 'middle portion thereof,

versely with respect to the thinner portion throughout its length; forming a blank by punching the same from said bar; pressmg said blank so as to bend the thicker portions thereof transversely with respect to the thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges for retaining said tooth body.

14. In a process of making a metallic denture backing adapted to hold a nonmetallic toothvbody; forming a blank by punching the same from a concave bar; pressing said blank so as to arch the thinner portion thereof in the direction of the axis of said bar, and bend the thicker portions thereof transthereof, to form a backing which is U- shaped 1n cross section, consldered transversely with respect to said bar, the bifurcations thereof forming opposite side flanges for retaining said tooth body.

15. In a processof maln'ng a metallic denture backingadapted to hold a nonmetallic tooth body; forming a blank by punching the same frorn'a concave bar; pressing said 7 blank so as to bend the thicker portions thereof transversely with respect to the thinner portion thereof, to form a backing which is U-shaped in cross section, considered transversely with respect to said bar,

the bifurcations thereof forming, opposite side flanges for retaining said' tooth body.

16. In a process of making a metallic denture structure; punching a concave bar to form "a blank; rendering the thicker portions of said blank less ductile than the thinnest portion thereof, by swaging them; i

and bending said thicker portions transversely to said thinnest portion, to form a recess between them. 7

' 17. In a process of making a metallic den ture structure; punching a concave bar-to form a blank; and bendingthe thicker-portions of said bar transversely to its thinnest portion, to form a recess between them.

In testimony whereof, I have hereunto signed my name at Wilkinsburg, Pennsyh Vania, this sixth day of November,'l918.

I ROBERT M. CRAIG..

Witnesses: i

R. A. COLEMAN, H. R. CRAIG. 

